1. Field of the Invention
The present invention relates to a vibration reducing technique of an impact tool such as a hammer and a hammer drill.
2. Description of the Related Art
(1st Known Art)
Japanese non-examined laid-open Patent Publication No. 2003-11073 discloses an electric hammer having a vibration reducing mechanism. This known electric hammer has a dynamic vibration reducer to reduce vibration caused in the axial direction of the hammer bit during hammering operation. The dynamic vibration reducer has a weight that can linearly move under a biasing force of a coil spring, and the dynamic vibration reducer reduces vibration of the hammer during hammering operation by the movement of the weight in the axial direction of the tool bit.
In the known electric hammer, the weight and the coil spring are disposed within a space having an annular section between a cylinder and a barrel part that houses the cylinder.
In the above-described arrangement and construction, component parts of the dynamic vibration reducer such as the weight and the coil spring need to be individually mounted to the cylinder or the barrel part. Thus, in the known electric hammer, further improvement is required in ease of assembly of the vibration reducing mechanism.
(2nd Known Art)
As another known art, a conventional electric hammer has a motor which linearly drives a hammer bit in the axial direction of the hammer bit. In a motor having a brush holder which is arranged on one end side of the motor along its axis of rotation and holds carbon brushes for supplying electric current, a motor cover is removably mounted for replacement of the carbon brushes which are consumables. A construction in which a motor housing for housing a motor is covered with a motor cover on the side of one axial end of the motor is disclosed, for example, in Japanese non-examined laid-open Patent Publication No. 2007-44869.
The known motor cover is designed and provided to cover the motor, particularly the brush holder and its surrounding region, and serves only as a cover.
(3rd Known Art)
As further another known art, Japanese non-examined laid-open Patent Publication No. 2004-174710 discloses a motor-driven power tool. In this known power tool, a controller is electrically connected to a driving motor by a plurality of lead wires, and power is supplied from a power source to the controller and then to a driving motor via the lead wires. In design of a power tool of this type, however, a further technique for improving ease of mounting electrical components such as a controller is required.